This invention relates generally to hypodermic needles and syringes, and more particularly the invention relates to a disposable, one-time or single use syringe and safety needle assembly. The safe, one-time use and subsequent disposal of hypodermic needles and syringes are immediate concerns in the medical and health professions. Accidental needle stick injuries following use of a syringe pose a significant risk to both patient, physician and nurse. The risk is a source of great anxiety due to the current HIV and hepatitis infection concerns of the general public. Thus, extreme care must be taken in the safe handling and disposal of used needles and syringes. Toward this end, the present invention represents a single use needle and syringe assembly. After the needle and syringe (hereinafter collectively referred to as a syringe) are once used, the mechanism of the present invention precludes further uses. It will, therefore, be more likely properly discarded than if further use were possible. Patient to patient cross contamination and drug user to drug user cross contamination are reduced.
The present invention is compact and, therefore, is capable of being implemented into syringes of extremely small size barrel capacity including syringes capable of administering dosages down to 1 cc. The prior art, on the other hand, as will be more fully explained hereinafter, cannot be easily and/or economically downsized while maintaining the effectiveness of the mechanisms and, therefore, they have not been commercially introduced in sizes smaller than standard 5 cc syringe bodies. The location of the locking mechanism in the prior art single use syringes enabled the device to limit the 5 cc conventional syringe to a maximum 1 cc dosage. However, it is clearly desired to have smaller maximum dosage syringes. It should be appreciated, however, that the present invention can also be adapted for use with 5 cc or other maximum dosage syringe barrels and, yet, the present invention has particular applicability to syringes of low dosage capacity.
The present invention provides a simple and inexpensive to manufacture mechanism for limiting the usage of a syringe (with or without needle) to one-time or single use only. The syringe is intended to be assembled at the manufacturing facility and provided to the physician (or nurse, patient, etc.) for use. The user fills the syringe with the appropriate medication in the conventional manner, i.e., by withdrawing the plunger with respect to the cylindrical barrel of the syringe, thereby drawing medication through the needle tip and into the barrel. Then, again, using a conventional technique, the needle is inserted to pierce the patient's skin. The plunger is manually moved with respect to the cylindrical barrel thereby forcing a piston toward the distal end of the syringe. The piston forces the medication out through the needle tip.
During the dosage administration portion of the procedure, according to the present invention, as will be more fully explained hereinafter, a locking spring travels along with the plunger shaft and, when it reaches the distal position, locking points are held against the interior sidewall of the cylindrical barrel to preclude a second retraction of the plunger with respect to the cylindrical barrel of the syringe. Thus, no further medication can be pulled into the syringe and, therefore, the syringe is incapable of being used a second time. A simple, single-use syringe is provided. The locking mechanism, precluding reuse, is automatic, i.e., it operates to block reuse without a conscious operation by the user to engage its operation.
It is also a feature of the present invention to provide the thumb-contacting portion of the syringe plunger as a break-apart disc such that, after use, the user of the syringe can simply bend or twist and remove the thumb-contacting disc and, thereby, further disable the syringe from a subsequent reuse. The ability of the thumb-contacting portion of the plunger shaft to become disengaged from the syringe also serves as a means of tracking inventory of the syringes.
It is another feature of the present invention to provide another mechanical locking device. This device, as well, blocks a second use of the syringe. It engages, however, only when the user deliberately desires to do so, by fully reciprocating the plunger to its maximum distal position. To effect this mechanical lock, the plunger and the thumb-contacting disc portion must be pushed fully toward the distal end of the syringe. When moved as described, the thumb-contacting disc portion and the plunger are locked (incapable of being withdrawn to draw in additional medication) by a male dove tail arrangement of the plunger which cooperates with a female dove tail of the barrel. Here, too, a safety mechanism is provided to prevent reuse of the syringe.
The present invention accomplishes the above objects by utilizing a new and unique plunger in association and in combination with a spring clip. The plunger comprises a plurality of cylindrical ratchet teeth. The spring clip is located by the manufacturer at a particular location on the plunger so as to limit maximum dosage of the syringe. In addition, the use of this new plunger and spring clip blocks reuse of the syringe. The construction can be incorporated into syringes of even 1 cc size without any loss of efficiency or safety.